Published Date
Composites Part A: Applied Science and Manufacturing March 2017, Vol.94:124–132, doi:10.1016/j.compositesa.2016.12.008 Author
Biao Zhang
Buyin Li,
Shenglin Jiang,
School of Optical and Electronic Information, Huazhong University of Science and Technology, No. 1037, Luoyu Road 1037, Wuhan 430074, China
Received 14 September 2016. Revised 5 December 2016. Accepted 7 December 2016. Available online 9 December 2016.
Abstract Poor sensitivity in low pressure regimes (<100 kPa) of pressure-sensitive rubbers (PSRs) is one of their major disadvantages compare to other piezoresistive materials. The reasons induced the poor sensitivity include bad dispersion and week interface of multi-walled carbon nanotubes (MWCNTs) applied in poly(dimethyl siloxane) (PDMS). A novel vinyl-terminated poly(dimethyl siloxane)-poly(phenylmethyl siloxane)-multi-walled carbon nanotubes (V-P-MWCNTs) with core-dualshell nanostructure is fabricated by noncovalently functionalized method. The V-P-MWCNTs as conductive fillers exhibits homogenous dispersion as well as good interfacial interaction in PDMS matrix. Slightly above the percolation threshold (0.19 vol.%), the PDMS-based nanocomposites with 0.2 vol.% of V-P-MWCNTs shows high piezoresistive sensitivity (22.16 × 10−3 kPa−1), high electrical conductivity (5.43 × 10−3 S/m) and low Young’s modulus (288.83 kPa). These results demonstrate that the V-P-MWCNTs are of great potential as the conductive fillers for improved piezoresistive sensitivity of PDMS nanocomposites, which can be potentially applied in the flexible touch sensors. Keywords
Published Date
Composites Part A: Applied Science and Manufacturing March 2017, Vol.94:133–145,doi:10.1016/j.compositesa.2016.12.003
Author
Preston B. McDaniel a,b,,
Subramani Sockalingam a,c
Joseph M. Deitzel a
John W. Gillespie Jr. a,b,c,d
Michael Keefe a,b
Travis A. Bogetti e
Daniel T. Casem e
Tusit Weerasooriya e
aCenter for Composite Materials, University of Delaware, DE, USA
bDepartment of Materials Science and Engineering, University of Delaware, DE, USA
cDepartment of Mechanical Engineering, University of Delaware, DE, USA
dDepartment of Civil and Environmental Engineering, University of Delaware, DE, USA
eUS Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, MD, USA
Received 13 July 2016. Revised 30 November 2016. Accepted 2 December 2016. Available online 5 December 2016.
Abstract The goal of this research is to understand the effect of fiber meso/nanostructure on the macroscopic quasi-static transverse compression response of ultra-high molecular weight polyethylene (UHMWPE) Dyneema SK76 fibers. These fibers exhibit nonlinear inelastic behavior with a small elastic limit and negligible elastic recovery upon unloading. Finite element model predictions of the experiment, using a continuum nonlinear inelastic constitutive description agree reasonably well with experimental force-displacement, but under-predict the contact area. The apparent fiber cross-sectional area is found to increase up to a maximum of 1.83 times the original area at 46% nominal strain. SEM and AFM images of the meso/nanostructure of the compressed fibers indicate the apparent area growth is due to fibrillation. This fibrillation results in the deformation of a fibril network causing non-uniform fibril nesting and nucleation of new nanoscale voids between fibrils. A comparison of UHMWPE and Kevlar KM2 fiber transverse compressive response is also discussed. Keywords
Published Date
Composites Part A: Applied Science and Manufacturing March 2017, Vol.94:113–123,doi:10.1016/j.compositesa.2016.11.027
Author
Dominik Dörr a,,
Fabian J. Schirmaier a
Frank Henning a,b
Luise Kärger a
aKarlsruhe Insititute of Technology (KIT), Institute of Vehicle System Technology (FAST), Department of Lightweight Technology (LBT), Karlsruhe, Germany
bFraunhofer - Institute of Chemical Technology (ICT), Pfinztal, Germany
Received 30 September 2016. Revised 24 November 2016. Accepted 25 November 2016. Available online 27 November 2016.
Abstract An approach for modeling rate-dependent bending behavior in FE forming simulation for either a unidirectional or a woven/bidirectional reinforcement is presented. The applicability of the bending model to both fiber architectures is guaranteed by introducing either an orthogonal or a non-orthogonal fiber parallel material frame. The applied constitutive laws are based on a Voigt-Kelvin and a generalized Maxwell approach. The bending modeling approaches are parameterized according to the characterization of thermoplastic UD-Tape (PA6-CF), where only the generalized Maxwell approach is capable to describe the material characteristic for all of the considered bending rates. A numerical study using a hemisphere test reveals that the Voigt-Kelvin approach and the generalized Maxwell approach lead to similar results for the prediction of wrinkling behavior. Finally, the approaches for modeling bending behavior are applied to a more complex generic geometry as an application test with a good agreement between forming simulation and experimental tests. Keywords
